Fixed .gitignore to use /install/ and /build/ with leading slash
so only the root-level colcon dirs are ignored, not
doc/lwc-doc/docs/sunrise/install/.
Adds install pages (Windows, Linux emulator, Linux workbench)
and 22 step-by-step screenshots that were never deployed.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
